Evaluation of Human Corneal Lenticule Quality After SMILE With Different Cap Thicknesses Using Scanning Electron Microscopy

Purpose: To evaluate the surface characteristics of lenticules created by small-incision lenticule extraction (SMILE) with different cap thicknesses. Methods: This prospective study included 20 consecutive patients who underwent bilateral SMILE. Surface regularity of the extracted corneal lenticule was analyzed using scanning electron microscopy (SEM) combined with 2 methods: qualitative and quantitative regularity. Qualitative regularity of SEM images was graded by masked observers using an established scoring system. Quantitative regularity of SEM images was assessed by counting the total number and areas of tissue bridges using Image-Pro Plus software. Four different cap thickness of 120, 130, 140, and 150 mm were compared. Refractive outcomes of patients were measured at baseline and 1 month after surgery. Results: As 10 specimens were not analyzable, only 30 eyes were included. Postoperatively, all eyes had postoperative uncorrected distance visual acuity of 20/20 or better; 43% had an unchanged corrected distance visual acuity; 43% gained 1 line; 10% lost 1 line. Ultrastructurally, surface irregularity was primarily caused by tissue bridges. The average surface regularity score obtained was 10.87 6 2.40 for 120 mu m, 10.78 +/- 2.60 for 130 mu m, 8.76 +/- 2.16 for 140 mu m, and 8.70 +/- 2.66 for 150 mu m (P, 0.001). The total number and areas of tissue bridges of 120 to 130 mu m were significantly less than 140 to 150 mu m (P < 0.05). Surface regularity decreased as cap thickness increased (P < 0.05). Conclusions: There is smoother appearance of the lenticular surface as seen through SEM when a thin cap is created compared with a thick cap qualitatively and quantitatively.